Chris, with modern forensics at the state they are at, no-knocks out of fear that evidence will be destroyed is ridiculous.
If the police are going to serve CSD's pot growing operation and they do so by knocking on the door and announcing themselves, then they hear the garbage disposal whir up, all they have to do is enter forcibly (a warrant grants this privilege if there is no response to an announcement), stop the disposal process, and test the disposal for residue. It'll be there, in spades.
The only justified use of a no-knock is in the case of violent kidnappers or hostage takers, or violent terrorists.
No-knocks for drugs? Blue collar stuff? SBR/AOW/MG/suppressor/AWB stuff? No way. The gun issues aren't illegal in and of themselves... that's essentially tax dodging is all. Blue collar. Non-violent. Drugs? The evidence will be there when you do a perfectly normal authoritarian and duly processed entry. Counterfeiting, money laundering, illegal gambling, prostitution and so on? What serves society better... a john who escapes the raid and continues to pay his income taxes, or a dead john and hooker when the boys in blue get trigger happy?